Having taken ambiguity to disturbing extremes in his slippery 2003 documentary "Capturing the Friedmans," director Andrew Jarecki unveils a very different true-crime saga in "All Good Things."

Having taken ambiguity to disturbing extremes in his slippery 2003 documentary “Capturing the Friedmans,” director Andrew Jarecki unveils a very different true-crime saga in “All Good Things.” Modeled on the strange story of Robert Durst, the wealthy Gothamite long suspected but never implicated in his wife’s 1982 disappearance, this feverishly creepy but dramatically miscalculated picture reps an unhappy marriage of murky psychodrama and dubious theorizing. Finally opening through Magnolia after a lengthy holdup by the Weinstein Co. (which ended with Jarecki buying back the rights), the long-gestating 2008 production will struggle to parlay mixed critical response into theatrical interest.

Marcus Hinchey and Marc Smerling’s script folds meticulous research and considerable speculation about the Durst affair into the tale of the singularly troubled David Marks (Ryan Gosling), scarred at a young age by his mother’s suicide and thereafter a perpetual disappointment to his intimidating father, Sanford (Frank Langella), the head of a seedy Manhattan real-estate empire. It’s 1971 when David courts Katie (Kirsten Dunst), a lovely young woman who seems to offer him an escape from his childhood demons. For her part, Katie sees in David a chance at a better life than she’s known growing up in Long Island.

The film is thus framed as a tragic love story between two opposites, as well as a close study of marital meltdown. After he and Katie spend a few happy years in Vermont, where they open a health-food store called All Good Things (hence the highly ironic title), David succumbs to his father’s pressure and enters the family business — a decision that causes both his psyche and his marriage to unravel. Spending his days collecting rent from porn theaters and massage parlors in Times Square (whose sordid ’70s ambience is vividly re-created here), David becomes increasingly cold, at times violent toward Katie, even forcing her to have an abortion when it’s clear he has no desire for children.

There’s much more to come, in an increasingly freakish and ominous story involving multiple homicide, concealment, cross-dressing and blackmail, as David flees New York for Galveston, Texas, and strikes up a bizarre friendship with reclusive lodger Malvern Bump (a terrific Philip Baker Hall) — who, like David’s friend Deborah (Lily Rabe) and even Katie herself, makes the mistake of seeing this scion of American privilege as an opportunity. The more the film implicates David, the more it distances itself and the viewer, playing out in the emotionally detached but sensationalistic, overripe manner of a tabloid freakshow.

The script’s wealth of exceedingly odd details suggests an attempt to hew close to known facts, an affirmation that truth is often stranger than fiction. But truth is a notion the film circles only vaguely and at times disingenuously, damning its central figure even as it conveniently falls back on the creative liberties afforded by dramatization. It’s hard to shake the feeling that “All Good Things,” like so many fact-fiction hybrids, would have been far more compelling as a straight documentary; Jarecki, who cleverly exploited a treasure trove of homevideo footage for “Capturing the Friedmans,” seems unable to marshal the resources of narrative filmmaking with the same verve.

As the decades-spanning story jumps around in time, Gosling is required to don a woman’s blonde wig one minute and layers of old-age makeup the next; while he’s ably cast as a man whose outward, baby-faced charm conceals darker impulses, the character is denied the psychological coherence that would invite not merely revulsion, but empathy. Dunst is entirely sympathetic as an optimistic young woman whose safety we instinctively fear for, and the film never quite recovers from her departure (whatever the reasons for the delayed release, it’s wonderful to see the actress onscreen again after a two-year absence). Langella is predictably imposing in a reductive domineering-dad role.

Michael Seresin’s 35mm lensing conveys a dark grit and texture redolent of pictures from the ’70s, and Wynn Thomas’ production design effectively spans a host of locations, from a humble Vermont market to a glassy Manhattan executive suite. Noisy score ratchets up the atmosphere to tediously operatic levels.